"Cramming books" could be a suitable antonym for "crack books". While "cracking books" means to study with dedication and intensity, "cramming books" refers to studying quickly and superficially, often before an exam. The difference between the two is that one involves a deep understanding of the material, while the other focuses on memorization. "Cramming books" is often considered a less effective way of studying, as the knowledge gained is not retained for very long. Therefore, for long-term learning and understanding, it's better to "crack books" rather than "cramming books".